Field machining of wind turbine gearboxes

ABSTRACT

A gearbox repair assembly is disclosed herein. The gearbox repair assembly includes a sleeve having an inner diameter configured to receive a bearing assembly and an outer diameter configured to fit within a bore of a gearbox housing. The gearbox housing can be part of a gearbox of a wind turbine. The gearbox repair assembly further includes a retaining plate configured to be attached to the gearbox housing for preventing an outer race of the bearing assembly from rotating in the bore relative to the gearbox housing. Also provided are methods to repair such a gearbox. The gearbox repair assembly and related methods reduce the time and cost needed to repair the gearboxes.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/968,267, filed Jan. 31, 2020, the contents of which are incorporatedherein by reference.

TECHNICAL FIELD

The disclosure relates generally to gearbox repair assemblies. Thisdisclosure also provides methods of repairing a gearbox, such as agearbox of a wind turbine.

BACKGROUND

There are many manufacturers of wind turbine gearboxes, and there are avariety of systemic problems related to the various types of gearboxes.One common problem is that bearings in the cast gearbox housings canbecome overloaded. This causes the outer race of the bearings to spin inthe housing bore, thereby causing misalignment of the gear teeth fromone drive component to another. If allowed to progress, this can causecatastrophic failure of the gearbox. In some cases, gear teeth can breakoff and travel throughout the rest of the drive train, causing evenfurther damage.

To address the problems described above, known solutions involvereplacing the gearbox with either a new or rebuilt unit. However, thisis a time-consuming process. Additionally, the expense of a replacementgearbox and the related crane and crews required to make thisreplacement are extremely high.

SUMMARY

A wind turbine gearbox repair assembly is disclosed herein. The windturbine gearbox repair assembly of the present disclosure allows forfield repair of wind turbine gearboxes. In some cases, the entire repairprocess can occur in a nacelle of the wind turbine. The illustrativewind turbine gearbox repair assembly drastically reduces the cost torepair wind turbine gearboxes at the site. It also reduces the timerequired to repair the gearbox and put it back into operation.

The wind turbine gearbox repair assembly may include a sleeve having aninner diameter configured to receive a bearing assembly and an outerdiameter configured to fit within a bore of a gearbox housing. Thegearbox housing may be part of a gearbox of a wind turbine. The windturbine gearbox repair assembly may further include a retaining plateconfigured to be attached to the gearbox housing for preventing an outerrace of the bearing assembly from rotating in the bore relative to thegearbox housing.

To repair such a gearbox, a surface of the gearbox housing can be cut soas to increase a size of a bore in the gearbox housing. Then, a sleeve,followed by a bearing assembly, can be installed in the bore. Thebearing assembly includes an outer race with an outer surface thatcontacts the sleeve when installed. A retaining plate can then beattached to the gearbox housing adjacent the bore. A retaining assemblycan be provided and may include a first portion that is part of theretaining plate and a second portion that is part of the bearingassembly. The retaining plate and the bearing assembly can be positionedrelative to one another such that the first and second portions of theretaining assembly are engaged so as to prevent the outer race of thebearing assembly from rotating in the bore relative to the gearboxhousing.

Inventive principles described herein may be incorporated into a varietyof different wind turbine gearbox repair assembly configurations. Thedetails of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of particular embodiments of thepresent invention and therefore do not limit the scope of the invention.The drawings are not necessarily to scale (unless so stated) and areintended for use in conjunction with the explanations in the followingdescription. Embodiments of the invention will hereinafter be describedin conjunction with the appended drawings, wherein like numerals denotelike elements.

FIG. 1 is a front perspective view of a portion of a wind turbinegearbox, partially cut-away so as to illustrate certain interiorcomponents of the gearbox.

FIG. 2 is a side view of two gears of a gearbox having gear teeth thatare misaligned between the two gears.

FIG. 3 is a perspective view of a portion of a wind turbine gearboxrepair assembly in use.

FIG. 4 is a detailed view of a bearing assembly in a bore of a gearboxhousing, showing a gap between the gearbox housing and the bearingassembly.

FIG. 5 is a perspective view of a bearing assembly of the presentdisclosure.

FIG. 6 is a front perspective view of a portion of a wind turbinegearbox that is similar to FIG. 1, except having a boring bar mounted tothe gearbox, and with both the piston and the bearing assembly removed.

FIG. 7 is a front perspective view of a gantry crane of the presentdisclosure.

FIG. 8 is a flow chart of an illustrative method of repairing a gearbox.

FIG. 9 is a perspective view of a boring bar.

DETAILED DESCRIPTION

The following detailed description is exemplary in nature and is notintended to limit the scope, applicability, or configuration of theinvention in any way. Rather, the following description provides somepractical illustrations for implementing exemplary embodiments of thepresent invention. Examples of constructions, materials, and/ordimensions are provided for selected elements. Those skilled in the artwill recognize that many of the noted examples have a variety ofsuitable alternatives.

The present disclosure relates to a gearbox repair assembly and relatedrepair methods. To facilitate an understanding of the presentdisclosure, a portion of a gearbox 10 is shown in FIG. 1. Specifically,a parallel stage of a drivetrain of a wind turbine gearbox is shownpartially cut-away so as to illustrate some of its interior components.The illustrated gearbox 10 has gears of various speeds and sizes,including, e.g., a low-speed gear 20, an intermediate gear assembly 25,and a high-speed pinion 30. When the gearbox 10 is in proper workingcondition, the gear shaft axes are parallel to each other, and thedifferent gears are aligned via their gear teeth 35. However, when thegear shaft axes are not exactly parallel, as shown in FIG. 2, the gearteeth 35 become misaligned and can cause catastrophic failure of thegearbox 10. Embodiments of the present disclosure are intended toprevent this type of situation from occurring.

The present disclosure provides a wind turbine gearbox repair assemblygenerally represented by reference numeral 100. As shown in FIG. 3, thewind turbine gearbox repair assembly 100 comprises a sleeve 200 havingan inner diameter configured to receive a bearing assembly 300 and anouter diameter configured to fit within a bore 40 of a gearbox housing45. The sleeve 200 can comprise any suitable material, such as castiron. In such embodiments, the gearbox housing 45 is part of a gearbox10 of a wind turbine.

The wind turbine gearbox repair assembly 100 is particularly useful whena gap 55 has formed between an outer race 310 of the bearing assembly300 and an inner diameter of the bore 40. Such a gap 55 is shown in FIG.4 and causes the outer race 310 of the bearing assembly 300 to rotate inthe bore 40. Due to pressure of the gear mesh and rotation of the outerrace 310 of the bearing assembly 300, the bearing assembly 300 will bepushed toward the gap 55. This causes misalignment of the gear teeth 35between different components of the gearbox 10 and can lead tocatastrophic failure of the gearbox 10.

When the outer race 310 of the bearing assembly 300 has previously spunin the bore 40, this can be visually detected by inspecting a plate notshown) located at a rear surface of the bore 40 behind where the bearingassembly 300 is located. When radial lines appear on the plate, thisprovides an indication that the outer race 310 of the bearing assembly300 has spun in the bore 40.

To repair a gearbox 10 having the gap 55 described above, the sleeve 200can be installed in the bore 40 to occupy the space formed by the gap 55and bring the bore 40 back to correct dimensional specifications. Thesleeve 200 can be secured in place using any conventional attachmentmeans, such as, but not limited to, spring pins. This will help preventthe outer race 310 of the bearing assembly 300 from spinning in the bore40.

As described in greater detail below, prior to installing the sleeve 200in the bore 40, the sleeve 200 can be cooled so as to shrink its outerdiameter. Then, after the sleeve 200 has been installed, a surface ofthe sleeve 200 can be cut until the inner diameter of the sleeve 200corresponds to an outer diameter of the bearing assembly 300, withinacceptable tolerances.

Since various types of gearboxes can be repaired using the presentrepair assembly 100 and related methods, skilled artisans willappreciate that the sleeve 200 can be cut to any size needed for aparticular gearbox. For any embodiment of the present disclosure, thebore 40 and the sleeve 200 can be cut so as to meet the standard rangesfor bearing size fit based on standards set by the American BearingManufacturers Association. According to such standards, the bearing fitwill vary depending on the particular bearing size.

The wind turbine gearbox repair assembly 100 further comprises aretaining plate 320 configured to be attached to the gearbox housing 45for preventing the outer race 310 of the bearing assembly 300 fromrotating in the bore 40 relative to the gearbox housing 45. Theretaining plate 320 can be attached to the gearbox housing 45 throughany suitable attachment means. As one non-limiting example, theattachment means can comprise a plurality of pins 330 (i.e., springpins), as shown in FIG. 3.

To better illustrate the various components, the retaining plate 320 isshown as transparent in FIG. 3. In some cases, the retaining plate 320includes a pin 340. The pin 340 is configured to project toward andengage a notch 345 in the bearing assembly 300 when the pin 340 is in anengaged position 350. The engaged position is shown in FIG. 3. The pin340 can be a spring pin or any other suitable type of pin that is ableto engage the notch 345 in the bearing assembly 300 and prevent theouter race 310 of the bearing assembly 300 from rotating in the bore 40.

As best shown in FIG. 5, the notch 345 can be formed in the outer race310 of the bearing assembly 300. A notch 355 can also be formed in thesleeve 200 (e.g., by drilling) and aligned with the notch 345 in thebearing assembly 300 such that the pin 340 engages both notches 345, 355when the pin 340 is in the engaged position 350. The reverseconfiguration is also contemplated, i.e., with the notch 345 insteadprovided in the retaining plate 320 and the bearing assembly 300configured to include a pin (similar to pin 340) that projects towardand engages the notch in the retaining plate 320.

In some embodiments, the wind turbine gearbox repair assembly 100comprises a cutting tool 400 configured to cut a surface 60 of thegearbox housing 45 such that the bore 40 in the gearbox housing 45 is ofsufficient size to receive the sleeve 200 therein. The cutting tool 400is used to increase the size of the bore 40 so that the bore canaccommodate the sleeve 200. Although not limiting, in many cases, thebore 40 will have an inner diameter of between about 2.5 inches andabout 16 inches. The plate located in the bore 40 behind the bearingassembly 300 can be used to help locate the center of the bore 40 formachining purposes.

The cutting tool 400 can be used manually or can be part of an automatedcutting process. In some cases, the cutting tool 400 comprises a boringbar 410 that accepts a tooling. Boring bars 410 are well-known in theart, and an exemplary boring bar 410 is shown in FIG. 9. Any suitableboring bar system can be used, such as the BB1750 and BB2250 portableline boring machines manufactured by Mactech, Inc. (Red Wing, Minn.). Asshown in FIG. 6, the boring bar 410 can be mounted to the gearbox 10 ofa wind turbine so as to facilitate machining of the bore 40. The boringbar 410 can be attached to the gearbox 10 through any type of attachmentmeans. In the embodiment shown in FIG. 6, for example, the boring bar410 is attached to the gearbox 10 by a first retaining plate 600. This,however, is by no means limiting.

The boring bar 410 includes a shank 610. In some cases, the shank 610can extend a distance of up to 36 inches so that the shank 610 is ofsufficient length to simultaneously extend into multiple bores (e.g.,both a rotor side and a generator side bore) of the gearbox housing 45.The boring bar 410 can be provided in various lengths, and in somecases, the boring bar 410 can extend up to 144 inches. The firstretaining plate 600, along with a second retaining plate 605, can bothbe attached to the shank 610.

The gearbox 10 may include an inspection port 615. As shown in FIG. 6,the inspection port 615 can have holes 618 so as to allow access toinspect the condition of the gearing. Prior to using the boring bar 410,the inspection port 615 can be removed from the gearbox 10 to allowaccess to the boring job and can also be used as a place to mount thesecond retaining plate 605. For example, the second retaining plate 605can be attached to a bottom of the inspection port 615.

The wind turbine gearbox repair assembly 100 can also comprise amicrometer configured to measure an inner diameter of the bore 40. Inuse, the micrometer can be positioned inside the bore 40 and turneduntil it touches the inner diameter of the bore 40. The resultingmeasurement can then be recorded.

In certain embodiments, the wind turbine gearbox repair assembly 100comprises a gantry crane 700. An exemplary gantry crane is shown in FIG.7. As is well-known in the art, a gantry crane 700 is an overhead cranethat includes a horizontal bridge 705 supported by A-frame legs 710. Thelegs 710 are often equipped with casters so that the crane 700 can beeasily moved as needed. Alternatively, a gantry crane 700 can ride alonga track installed on a ground surface.

The gantry crane 700 of the present disclosure can advantageously bebuilt so as to fit in a nacelle of the wind turbine above the gearbox10. When provided, the gantry crane 700 is configured to remove thegearbox housing 45 from the gearbox 10 and to facilitate repair of thegearbox housing 45 in the nacelle of the wind turbine. When the gantrycrane 700 is installed in the nacelle, the entire repair process can beperformed in the nacelle.

In many embodiments, the gantry crane 700 comprises one or morematerials that are both strong and lightweight. This enables the gantrycrane 700 to be strong enough to lift large portions of the gearbox 10so as to facilitate repair of the gearbox 10, while also beinglightweight enough that components of the gantry crane 700 can be takeninto the nacelle and the gantry crane 700 assembled in the nacelle. Inmany cases, the gantry crane 700 comprises a lightweight metal (e.g.,aluminum) or a lightweight metal alloy. If the gantry crane comprises aheavier material (e.g., steel), the gantry crane 700 may be too heavy tobe lifted by technicians and installed in the nacelle. Thus, the gantrycrane 700 should either be devoid of heavy materials, or any such heavymaterials should be present in components of the gantry crane 700 inrelatively low amounts, such that the gantry crane 700 is stilllightweight enough to be easily handled by technicians.

Skilled artisans will appreciate that a gantry crane 700 is not requiredin all embodiments. Instead, in other cases, a crew and a conventionalcrane can be mobilized to the site when needed and used to lower thegearbox housing 45 down to the ground for repair. However, this is lessdesirable than using a gantry crane 700, since repair with aconventional crane can add significant time and cost. Furthermore, sucha crane may not always be available when the repair is needed.

An illustrative method 800 of repairing a gearbox is shown in FIG. 8.The method 800 can include the step 805 of using a crane to remove agearbox housing from a gearbox. In some cases, the gearbox can be partof a wind turbine, as discussed above. Various types of cranes can beused for this purpose. In some cases, the crane can comprise a gantrycrane installed above the gearbox. In some such cases, the gantry cranecan be in the nacelle of the wind turbine.

Skilled artisans will appreciate that step 805 is not required in allcases. In some instances, depending on the gearbox make and model, thegearbox housing and the gearbox do not need to be separated from eachother in order to complete the repair.

The method 800 can also include the step 810 of removing a bearingassembly from a bore of the gearbox housing. As noted, the bearingassembly may be damaged from overpressure. This enables a replacementbearing assembly to be installed in the bore in a later step of themethod 800.

The method 800 can include the step 815 of cutting a surface of thegearbox housing so as to increase a size of a bore in the gearboxhousing. In certain embodiments, cutting the surface of the gearboxhousing is performed with a boring bar. In such cases, the boring barcan be mounted to the gearbox, e.g., by a retaining plate, as describedabove. In embodiments where a crane is used to remove the gearboxhousing from the gearbox, such step is performed prior to cutting thesurface of the gearbox housing.

After cutting the surface of the gearbox housing, the method 800 caninclude the step 830 of installing a sleeve in the bore. Thus, it isimportant that in step 815, the surface of the gearbox housing be cut sothat the bore is of sufficient size to receive the sleeve. The sleevecan comprise any suitable material, such as cast iron. The sleeve can besecured in place, e.g., using pins, such as spring pins.

To ensure the sleeve will fit tightly in the bore, the method 800 caninclude the step 820 of measuring an inner diameter of the bore. Thisstep can be performed using any suitable measuring instrument. In someinstances, a micrometer can be used to measure the inner diameter of thebore using the techniques described above.

The method 800 can also include the step 825 of cooling the sleeve priorto installing the sleeve in the bore. In some cases, this can involvechilling or freezing the sleeve, e.g., by placing the sleeve in afreezer or in dry ice, or by spraying the sleeve with liquid nitrogen.This will shrink an outer diameter of the sleeve so that it can easilyfit in the bore, without damaging or distorting the sleeve.

The method can also include the step 835 of installing a bearingassembly in the bore. This bearing assembly is intended to replace thebearing assembly that was removed in step 810. The replacement bearingassembly includes an outer race with an outer surface that contacts thesleeve when installed. In some cases, the replacement bearing assemblyis installed in the sleeve before the sleeve is installed in the bore.In some cases, the sleeve is installed in the bore before thereplacement bearing assembly is installed in the sleeve.

After the sleeve and the bearing assembly are installed in the bore, themethod 800 can include the step 840 of attaching a retaining plate tothe gearbox housing adjacent the bore. The retaining plate can retainthe sleeve and the bearing assembly in the bore.

When the retaining plate is properly attached to the gearbox housing, aretaining assembly is configured to prevent the outer race of thebearing assembly from rotating in the bore. In particular, the retainingassembly can include a first portion that is part of the retaining plateand a second portion that is part of the bearing assembly. In certainembodiments, one of the first and second portions of the retainingassembly comprises a pin and the other of the first and second portionsof the retaining assembly comprises a notch. In embodiments of thisnature, the retaining plate and the bearing assembly are positionedrelative to one another such that the first and second portions of theretaining assembly are engaged (i.e., the pin engages the notch) so asto prevent the outer race of the bearing assembly from rotating in thebore relative to the gearbox housing. In some cases, the first portionof the retaining assembly comprises the pin and the second portion ofthe retaining assembly comprises the notch such that the notch isprovided in the bearing assembly and the retaining plate includes thepin. Although the retaining assembly has been described herein as a pinand notch, other configurations that are suitable for the same purpose(i.e., preventing the outer race of the bearing assembly from rotatingin the bore) can alternatively be used.

In embodiments where a gantry crane is used, various steps of the method800, including cutting the surface of the gearbox, installing thesleeve, installing the bearing assembly, and attaching the retainingplate, can all occur in a nacelle of the wind turbine. This is both lesstime-consuming and less costly than having to repair a wind turbinegearbox on the ground.

The method 800 can also include the step 845 of aligning the pluralityof gear teeth between different components of the gearbox. This willensure that the gears are in proper alignment with respect to eachother.

Various examples have been described with reference to certain disclosedembodiments. The embodiments are presented for purposes of illustrationand not limitation. One skilled in the art will appreciate that variouschanges, adaptations, and modifications can be made without departingfrom the scope of the invention.

The invention claimed is:
 1. A method comprising: cutting a surface of agearbox housing so as to increase a size of a bore in the gearboxhousing, the gearbox housing being part of a gearbox; installing asleeve in the bore; installing a bearing assembly in the bore, thebearing assembly including an outer race with an outer surface thatcontacts the sleeve when installed; and attaching a retaining plate tothe gearbox housing adjacent the bore; wherein a retaining assembly isconfigured to prevent the outer race of the bearing assembly fromrotating in the bore, the retaining assembly including a first portionthat is part of the retaining plate and a second portion that is part ofthe bearing assembly, and wherein one of the first and second portionsof the retaining assembly comprises a pin and the other of the first andsecond portions of the retaining assembly comprises a notch, wherein theretaining plate and the bearing assembly are positioned relative to oneanother such that the pin engages the notch so as to prevent the outerrace of the bearing assembly from rotating in the bore relative to thegearbox housing.
 2. The method of claim 1, wherein the first portion ofthe retaining assembly comprises the pin and the second portion of theretaining assembly comprises the notch.
 3. The method of claim 1,wherein the cutting of the surface of the gearbox housing is performedwith a boring bar.
 4. The method of claim 1, wherein the gearbox is partof a wind turbine.
 5. The method of claim 4, further comprising, priorto cutting the surface of the gearbox housing, using a crane to removethe gearbox housing from the gearbox.
 6. The method of claim 5, whereinthe crane comprises a gantry crane, and wherein cutting the surface ofthe gearbox, installing the sleeve, installing the bearing assembly, andattaching the retaining plate all occur in a nacelle of the windturbine.
 7. The method of claim 1, further comprising cooling the sleeveso as to shrink an outer diameter of the sleeve prior to installing thesleeve in the bore.
 8. The method of claim 1, wherein the gearbox has aplurality of gear teeth, the method further comprising aligning theplurality of gear teeth between different components of the gearbox.